* {
    margin: 0;
    padding: 0;
}

#demo {
    width: 429px;
    height: 255px;
    margin: 50px;
    position: relative;
    border: 1px solid #ccc;
}

#small_box {
    position: relative;
    z-index: 1;
}

#float_box {
    display:none;
    width: 160px;
    height: 120px;
    position: absolute;
    background: #ffffcc;
    border: 1px solid #ccc;
    opacity: 0.5;
    cursor: move;
}

#big_box {
    display:none;
    position: absolute;
    top: 0;
    left: 460px;
    width: 450px;
    height: 400px;
    overflow: hidden;
    border: 1px solid #ccc;
    z-index:1;
}

#big_box img {
    position: absolute;
    z-index: 5;
}